ROCKVILLE, Md. -- Friday's crash involving a MARC train and a pregnant driver who got caught crossing the railroad tracks prompted authorities to remind drivers never to attempt to cross tracks unless there already is sufficient room between the crossing and the next vehicle on the other side of the tracks. Cemille Valencia's car was struck after the gates came down on her car. She said traffic was moving along at a steady pace but just stopped suddenly, leaving her stuck on the tracks at Randolph Road in Rockville. The conductor tried to stop, but it was too late, and...